Many products, including prescription drugs, over the counter drugs (e.g., analgesics) and vitamins, come in a solid dosage (i.e., "medicament") form. Two common shapes for these medicaments are referred to as "tablets" and "caplets". Tablets are generally disc-shaped having a diameter that is greater than their height. Caplets are elongated shapes having a longitudinal axis that is greater than the greatest thickness of the medicament along the longitudinal axis, typically by approximately 2.5 times. Both usually include rounded ends and edges and a flat surface corresponding to the walls of the die in which the mixture of ingredients are pressed into the particular solid dosage form. The flat area is sometimes referred to as a sidewall and can form a corner or edge relative to the two sides on opposite sides of the sidewall.
A common problem with both caplets and tablets (collectively "medicaments") is the texture or feel of their surfaces. Without any outer coating, both forms have a "chalky" texture formed by the compressed mixture. Research has established that some people believe uncoated medicaments are difficult to swallow. Research also has found, however, that people believe that medicaments having a gelatin or similar coating are significantly easier to swallow. Accordingly, many such processes have been developed and are known in the art.
One such process, disclosed in U.S. Pat. No. 599,865, utilizes a bar or plate which has been coated with a cleanly separable adhesive preparation, such as a combination of beeswax and rosin. Medicaments to be coated are pressed onto the adhesive and partially dipped into a coating mixture. The medicaments may then be dried and pressed onto a second adhesive coated bar or plate so that the remaining portions of the medicaments may be dipped.
U.S. Pat. No. 540,538 discloses a machine for dipping medicaments which utilizes a plate having countersunk holes to retain tablets by the application of a vacuum through the holes. The plate is placed over a vacuum box and medicaments are placed in each hole. A vacuum is then applied and the box and plate are inverted, thereby allowing the medicaments to be dipped in a coating bath. Once the medicaments have been dipped, the box is returned to its upright position, the vacuum is removed and the plate is manually removed, with the medicaments in place, to allow drying of the coating. After drying, the medicaments may be transferred onto a second plate with their uncoated sides exposed by manually placing the second plate over the medicaments contained on the first plate and flipping the two plates over. The uncoated sides may then be coated as described above.
Another process, disclosed in Japanese Patent Publication No. 41-13997, utilizes rigid tubes to retain tablets on their ends by the application of a suction force through the tube center. After dipping the tablets to approximately their midpoints and drying, the tablets are inverted and transferred onto opposing tubes. The vacuum is then switched from the first set of tubes to the second thereby exposing the uncoated portions of the tablets to be dipped. A drawback of this system is that no means is provided to easily center the tablets on the tubes.
U.S. Pat. No. 2,373,721 refers to a system for coating medicaments in which the medicaments are held over a coating tank in an inverted orientation by suction tubes. Cups slightly larger than the individual medicaments are then raised from an initial position, submerged in the coating, to immerse the individual medicaments in coating material contained within the cups.
U.S. Pat. No. 4,965,089 refers to the use of a caplet holding plate having sets of caplet gripping collets on both sides thereof. Caplets, initially disposed on one side of the plate, are dipped in a gelatin coating on one end then pushed through the plate so that the other side of the caplet may be coated. The disadvantages of such a system are that the caplet holding plate is not suitable for coating tablets having a height substantially less than their diameter. In addition, the coated surface may be damaged when pushed through the collet to the other side of the caplet holding plate.
U.S. Pat. No. 5,228,916, refers to the use of moveable vacuum tubes, which extend through a carrier plate, to secure tablets to be dipped. Such a process is not, however, well suited for coating caplets whose ends may not be readily secured to a vacuum tube. In addition, the use of multiple moveable vacuum tubes makes it difficult to maintain the tablets centered on the vacuum tubes in a level plane parallel with the surface of the coating in which the tablet is to be dipped. It is, therefore, difficult to obtain a level transition line when coating tablets with more than one color coating.
Therefore, there exists a need for a medicament coating system which may be easily adapted to coat medicaments of different sizes and shapes and which produces a uniform coating with no damage to the finished product.